/**
 *    Copyright 2009-2018 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package com.yinsin.jpabatis.reflection;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

import com.yinsin.jpabatis.annotations.Param;
import com.yinsin.jpabatis.binging.MapperMethod.ParamMap;
import com.yinsin.jpabatis.config.Configuration;
import com.yinsin.jpabatis.session.ResultHandler;
import com.yinsin.jpabatis.session.RowBounds;

public class ParamNameResolver {

	private static final String GENERIC_NAME_PREFIX = "param";

	/**
	 * <p>
	 * The key is the index and the value is the name of the parameter.<br />
	 * The name is obtained from {@link Param} if specified. When {@link Param}
	 * is not specified, the parameter index is used. Note that this index could
	 * be different from the actual index when the method has special parameters
	 * (i.e. {@link RowBounds} or {@link ResultHandler}).
	 * </p>
	 * <ul>
	 * <li>aMethod(@Param("M") int a, @Param("N") int b) -&gt; {{0, "M"}, {1,
	 * "N"}}</li>
	 * <li>aMethod(int a, int b) -&gt; {{0, "0"}, {1, "1"}}</li>
	 * <li>aMethod(int a, RowBounds rb, int b) -&gt; {{0, "0"}, {2, "1"}}</li>
	 * </ul>
	 */
	private final SortedMap<Integer, String> names;

	private boolean hasParamAnnotation;

	public ParamNameResolver(Configuration config, Method method) {
		final Class<?>[] paramTypes = method.getParameterTypes();
		final Annotation[][] paramAnnotations = method.getParameterAnnotations();
		final SortedMap<Integer, String> map = new TreeMap<>();
		int paramCount = paramAnnotations.length;
		// get names from @Param annotations
		for (int paramIndex = 0; paramIndex < paramCount; paramIndex++) {
			if (isSpecialParameter(paramTypes[paramIndex])) {
				// skip special parameters
				continue;
			}
			String name = null;
			for (Annotation annotation : paramAnnotations[paramIndex]) {
				if (annotation instanceof Param) {
					hasParamAnnotation = true;
					name = ((Param) annotation).value();
					break;
				}
			}
			if (name == null) {
				// @Param was not specified.
				if (config.isUseActualParamName()) {
					name = getActualParamName(method, paramIndex);
				}
				if (name == null) {
					// use the parameter index as the name ("0", "1", ...)
					// gcode issue #71
					name = String.valueOf(map.size());
				}
			}
			map.put(paramIndex, name);
		}
		names = Collections.unmodifiableSortedMap(map);
	}

	private String getActualParamName(Method method, int paramIndex) {
		return ParamNameUtil.getParamNames(method).get(paramIndex);
	}

	private static boolean isSpecialParameter(Class<?> clazz) {
		return RowBounds.class.isAssignableFrom(clazz) || ResultHandler.class.isAssignableFrom(clazz);
	}

	/**
	 * Returns parameter names referenced by SQL providers.
	 */
	public String[] getNames() {
		return names.values().toArray(new String[0]);
	}

	/**
	 * <p>
	 * A single non-special parameter is returned without a name. Multiple
	 * parameters are named using the naming rule. In addition to the default
	 * names, this method also adds the generic names (param1, param2, ...).
	 * </p>
	 */
	public Object getNamedParams(Object[] args) {
		final int paramCount = names.size();
		if (args == null || paramCount == 0) {
			return null;
		} else if (!hasParamAnnotation && paramCount == 1) {
			return args[names.firstKey()];
		} else {
			final Map<String, Object> param = new ParamMap<>();
			int i = 0;
			for (Map.Entry<Integer, String> entry : names.entrySet()) {
				param.put(entry.getValue(), args[entry.getKey()]);
				// add generic param names (param1, param2, ...)
				final String genericParamName = GENERIC_NAME_PREFIX + String.valueOf(i + 1);
				// ensure not to overwrite parameter named with @Param
				if (!names.containsValue(genericParamName)) {
					param.put(genericParamName, args[entry.getKey()]);
				}
				i++;
			}
			return param;
		}
	}
}
